Older adults are expected to comprise 25% of the workforce in the US by the year 2050. Successful employment of older adults and subsequent maintenance of their independence and health depends on their ability to perform and learn novel motor tasks with accuracy. The effects of human aging on cognition and fine motor performance have been studied extensively. Nonetheless, the interaction of the age-associated motor impairments and ability to learn and retain novel motor tasks is not well understood. Based on our preliminary work, we hypothesize that the ability of older adults to learn novel fine motor tasks is compromised due to altered agonist-antagonist activation and that training that emphasizes alternating agonist- antagonist activity will improve the ability of older adults to retain and transfer novel motor tasks. The hypothesis will be tested with three specific aims. The first two specific aims will identify neuromuscular mechanisms that contribute to the impaired ability of older adults to learn and transfer novel motor tasks during single-joint movements. The first experiment (Aim 1) will identify the agonist-antagonist adaptations that occur in young and older adults at the single motor unit level when learning and transferring dexterous motor tasks with the index finger. The second experiment (Aim 2) will identify the neural adaptations that occur in young and older adults at the agonist-antagonist muscle level when learning and transferring novel aiming motor tasks. The third experiment (Aim 3) will extend the findings to a multi-joint task and determine the efficacy of a speed-progressive light-load training protocol in improving the ability of older adults to learn and transfer fine novel motor tasks with single-joint and multi-joint movements. We expect to find that the ability of older adults to learn, retain, and transfer fine novel motor tasks with accuracy is impaired because of altered activation of the agonist-antagonist motor neuron pool. This impairment in activation will be evident at the single motor unit and whole muscle level and will be exacerbated during multi-joint movements. Finally, we expect that the proposed speed-progressive light-load training will improve the ability of older adults to perform, retain, and transfer fine novel motor tasks with single-joint and multi-joint movements. The findings of this project, therefore, could have a significant impact on the development of motor rehabilitation strategies for young and older adults, as well for individuals who suffer from neurological disorders that impair movement accuracy. PUBLIC HEALTH RELEVANCE The ability to learn new motor tasks is a fundamental adaptive component of life. Consequently older adults who cannot adapt to changing environments by learning new motor tasks will loose their independence and health. Furthermore, older adults are expected to comprise 25% of the workforce in the US by the year 2050. It is crucial, therefore, to understand how the healthy aging neuromuscular system learns to accomplish accurate movements and identify ways to improve the ability of older adults to learn and perform motor tasks with accuracy. The findings of this project, therefore, will identify neuromuscular mechanisms that contribute to motor learning and could have a significant impact on the development of training protocols and motor rehabilitation strategies for young and old adults.